Article II, Section 1 of the Constitution specifies the oath the president takes in assuming the responsibilities of this highest executive office: "I do solemnly swear (or affirm) that I will faithfully execute the Office of President of the United States, and will to the best of my ability, preserve, protect, and defend the Constitution of the United States."

George Washington took the oath with his hand on a Bible, and almost all other presidents have followed his example. Most use a special family Bible, leaving it open to a passage that has particular meaning for them. Traditionally the Chief Justice of the United States administers the oath, but in cases when vice presidents have assumed the presidency because of a death, others do the honors. When Warren G. Harding’s death elevated Calvin Coolidge to the presidency, his father, a justice of the peace, administered the oath.

A president whose term begins on Sunday takes the oath privately on that day, and repeats it in a public ceremony the next day. The solemnity of the swearing-in ceremony seems to reflect the importance the Founders attached to the executive office.